1. Field of the Invention
The present invention relates to a siloxane polyimide and a heat-resistant adhesive containing the same, and more particularly to a solvent-soluble siloxane polyimide and heat-resistant adhesive containing the same.
2. Description of Related Art
Heat-resistant adhesives containing an aromatic polyimide, etc. as a main component have been so far used in bonding between a base material and a copper foil of a flexible printed substrate. However, the aromatic polyimide is generally insoluble in ordinary organic solvents, and thus is used in the form of a solution of an aromatic polyamic acid as its precursor, which specifically requires an additional polyimidization reaction step with heating at a high temperature for a long time in stage B of evaporating coating solution and ring closure reaction for polyimidization. The polyimidization reaction step has such problems as occurrence of void phenomena and thermal deterioration of electronic parts per se.
JP-A-61-118424, JP-A-1-121325, etc. on the other hand, disclose solvent-soluble siloxane polyimides, but have such problems as low heat resistance, insufficient solubility in a variety of organic solvents, considerable curling of substrates when drying solution-applied flexible printed substrates, etc.